1. Field of the Invention
The present invention relates to a spacer mount in a gas-discharge display device in which glass elements are arranged between a control hole plate and a fluorescent screen.
2. Description of the Prior Art
In a gas discharge display device (plasma display) in the execution of a so-called flat picture screen, such as is described, for example, in the German published application No. 24 12 869, the spacer mount between the control hole plate and the fluorescent screen represents a difficult problem because this spacing must be observed with great precision over the entire picture screen surface. Together with the size of the control plate holes, it determines the penetration factor of the high voltage electrode at the front plate to the control electrodes and, therefore, the steepness of the individual image points.
Solutions for this problem have been proposed in the German published application No. 26 15 721. Support bars consisting of insulating material seal to the spacer mounting. It has already also been proposed in German application No. P 27 50 587 to provide meander-like glass strips or a honeycomb-like glass element as spacing elements between the control hole plate and the fluorescent screen.
A further proposal of German patent application No. P 28 02 976.7 proceeds from an advantageous manufacturing method for perforate plates and provides a plurality of thin, perforate glass plates lying on top of one another. The perforations are formed by means of etching. In order that the unavoidable lateral undercuttings remain small, thin glass plates are individually etched, i.e. care is taken that the individual etching operation must only create a small depth. The lateral undercutting which thereby arises is relatively great for the individual etching depth, but not with respect to the entire depth of the holes which are aligned atop one another. This is of great advantage in view of the high tolerance requirements. For example, the spacing to be observed is in the magnitude of 1 mm and, therefore, likewise the thickness of the spacer mount and the depth of the holes therein. The thickness of the bridges between the holes, however, should not exceed 0.1 mm, because the holes must be sufficiently large, on the one hand, and, on the other hand, must be present in a sufficient quantity. One hole must be present per image point (the total number derives from 625 lines.times.1500 columns) and all holes must be uniformly spaced from one another.
According to this proposal, the entire so-called post-acceleration space between the control hole plate and the fluorescent screen is filled with a glass element, except for the holes provided for the electron paths passing therethrough. By so doing, the spacing can be reliably observed over the entire surface of the fluorescent screen. Due to the relatively narrow holes in the insulation body, however, problems occur with respect to the field distribution. The walls of the holes and the glass can be statically charged, both due to scattered primary electrons, as well as due to secondary electrons proceeding from the fluorescent screen. Inhomogeneities arise within the electric field between the control hole plate and the (post-acceleration) anode lying on the fluorescent screen, which inhomogeneities can prevent, in the extreme case, the pentration of the electrons to the fluorescent screen. This is all the more true because, in the flat structure, the acceleration voltages cannot be very high and the electrons are therefore low-energy electrons.